Exposure to light at night accelerates aging and spontaneous uterine carcinogenesis in female 129/Sv mice

Figures & data

Table 1. Body weight gain dynamics in female 129/Sv mice exposed to various light regimens

	Body weight (g) at the age of:
Light/dark regimen	5 mo	9 mo	13 mo	18 mo	20 mo	23 mo	25 mo
LD	23.4 ± 0.3	24.8 ± 0.4	24.7 ± 0.1	26.0 ± 0.5	26.6 ± 0.3	27.0 ± 0.3	28.7 ± 0.4
LL	23.3 ± 0.3	23.1 ± 0.13^b	25.5 ± 0.3^a	29.8 ± 0.3^b	31.6 ± 0.5^b	32.6 ± 0.5^b	35.4 ± 0.8^b

The difference with the LD is significant, ^ap < 0.05; ^bp < 0.01, the Student’s t-test.

Table 2. Parameters of estrous function in female 129/Sv mice exposed to various light regimens

			Rate of estrous cycles of various length, %
Age (months)	Number of mice	Length of estrous cycles (days)	< 5 d	5–7 d	> 7 d	Fraction of mice with irregular estrous cycles (%)
LD
6	46	6.4 ± 0.14	0	76.7	23.3	8.7
10	46	6.5 ± 0.13	0	76.7	23.3	10.9
13	45	6.3 ± 0.24	3	73.5	23.5	20.0
20	36	6.1 ± 0.31	7.1	78.6	14.3	8.3
LL
6	46	6.7 ± 0.15	0	82.0	18.0	15.2
10	46	6.8 ± 0.23	3.7	77.8	18.5	45.7^a
13	44	6.6 ± 0.39	5.6	83.5	11.1	54.5^a
20	38	7.3 ± 0.44*	0	58.3	41.7	68.4^a,b

^a The difference with the LD is significant, p < 0.05; the Fischer exact test. ^bThe difference with the LL age of 6 mo is significant, р < 0,05.

Table 3. Survival distribution in female 129/Sv mice exposed to various light regimens

	Number of survivors at the age of: (days)
Group	300	400	500^a	550	600	650	700	750	800	850	900	950	1000
LD	46	46	43	42	38	34	32	27	22	14	10	2	0
LL	46	43	41	38	38	34	28^b	20^b	13^b	3^b	1^a	0	0

^a The first tumor detected in this interval. ^bThe difference with the controls of corresponding age is significant, p < 0.05; Fischer’s exact test.

Figure 2. Effect of the exposure to the constant illumination (LL) on survival and tumorigenesis in female 129/Sv mice. Abscissa, age, days. (A) Survival. Ordinate, number of mice, %. (B) Age-dependent tumor rate curves. Ordinate, number of tumor-bearing mice, %.

Table 4. Parameters of the lifespan and tumorigenesis in female 129/Sv mice exposed to various light regimens

	Light regimen
Parameters	LD	LL	Ratio
Number of mice	46	46
Mean lifespan (LS), days	763 ± 21.8	701 ± 20.7^a	−8.1%
Median	795	722	−9.2%
Mean LS of last 10% survivors	967 ± 10.2	867 ± 11.0^b	−10.3%
Maximum lifespan, days	997	902	−9.5%
Aging rate (α), days^−3	7.97 (6.74; 8.23)	9.39 ^a (8.83; 10.9)	+1.2 times
MRDT, days	87 (84; 103)	74^a (63; 79)	−1.2 times
The age of the 1st tumor detection, days	500	442
Effective number of mice	45	43
Number of tumor-bearing mice	37 (86.7%)	35 (81.4%)
Number of fatal tumor-bearing mice	31 (68.9%)	23 (53.5%)
Mean LS of tumor-bearing mice, days	800 ± 20.6	745 ± 17. 4^a	−6.9%
Localization and type of tumors
Uterus:
hemangioma	6	12	p = 0.065
sarcoma	30	20	p = 0.079
Malignant lymphoma	1	2
Lung:
adenoma	-	2
adenocarcinoma	1	1
Stomach: adenocarcinoma	1	-
Bladder: papilloma	-	1

The difference with the control of the LL: ^ap < 0.05; ^bp < 0.001.

Figure 1. Macro- and microphotograph of uterine sarcoma in 129/Sv mice exposed to constant light regimen (H and E, ×320).